In optical communications, optical signals carry information. For example, a transmitter in an optical or optoelectronic transceiver converts one or more electrical signals into optical signals, and a receiver in an optical or optoelectronic transceiver converts one or more optical signals into electrical signals. An objective of optical communication research and development is to increase and/or maximize bandwidth to the greatest extent possible.
At a given baud rate, the capacity of a transmitter or receiver in an optical transceiver may be limited by the number of optical channels (or wavelengths for wavelength division multiplexing systems) that a single transmitter optical subassembly or receiver optical subassembly can contain. When conventional optical components are used to multiplex and/or demultiplex a multi-channel optical signal, a minimal size and reliability are primary concerns about the system processing such signals.
As a number of multiplexed/demultiplexed channels increases, the size of the system grows considerably, in a transverse direction and/or a longitudinal direction. Where a single zig-zag path is used to combine all of the optical channels, several issues typically arise. For example, the difference in the optical path length becomes relatively large between the first channel and the last channel, making the design and alignment of lenses more difficult. Any pitch error that may arise accumulates over the increased number of channels. For example, if the first channel in an N-channel system has a small error, the error can be N times greater at the last channel. In other words, ensuring good performance becomes more difficult for each additional channel. Furthermore, the increasing size due to the increasing number of channels is undesirable, given the fixed dimensions of standard optical transceiver packages. Larger systems are also more vulnerable to index variations due to changes of temperature and/or pressure.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.